Automatic electric plug



July 15, 1930 s. JsTAvRAcos 1,770,715

AUTOMATIC ELECTRIC lPLUG Filed Aug. 3. 1927 IN ENTOR. W gn B L 4/ yM A TTORNEYS.

Patented July 15, 1930 PATENT OFFICE GEORGE J. STVAVRACOS, OF NEW YORK, N. Y.

AUTOMATIC ELECTRIC PLUG Application tiled August 3, 1927.

This invention relates to a plug which may be inserted in a line between an electric source of power and an electrical heating device such as the well known electric iron, and

[ which contains means for automatically regulating the heat of the device by opening and closing the circuit thereto.y

The invention will be best understood from the following description and the accompanying drawing, inwhich the figure is a longitudinal view through a plug constructed according to my invention, with the electrical connections shown diagrammatically.

In the selected embodiment which I have shown in the drawing, the numeral l designates a portion of a body of insulating material forming a plug, within which the invention may be received. Plugs of this nature are usually made in two parts, fastened together by bolts or the like, and I have shown one of these parts provided with the holes 2, which may receive such bolts to unite y it with a corresponding part.

The neck 3 of the plug is provided with the usual recess 4 to receive a coil spring surrounding a cord. At the other end of the plug are provided two holes 5 which are in registry with the usual contacts 6 which form sockets for the reception of plugs on an elec tric iron or other heating device. Passing through the neck 3 are the usual pair of conductors 7 and 8,v which' are normally received in the usual cord which connects the plug to a source of current. The conductor y7 is connected in parallel to thecontacts 9 and 10 of a four-pole switch, theother two poles of which are shown at lland 12. y

Pivoted centrally of the contacts 9, 10, 11

u The solenoid 17 has a circuit formed in two and 12, is a contact member 13 having rigidly Serial No. 210,281.

branches, both of which are disposed in parallel with the heating circuit which has just been described. One of these branches leaves the conductor 19 at 20, and includes a contact 21, a second Contact 22 mounted upon a :55l thermostat 23, the conductor 24, the solenoid 17 and the conductor 25 which connects the solenoid to the conductor 8. The other branch comprises the contacts l0 and 12, the conductor 26, the contacts 27 and 22, the con- 601 ductor 24, solenoid 17 andthe conductor 25.

The thermostat 23 is supported between two relatively heavy plates 28, these plates being of heat conducting material. The thermostat is, however, electrically insulated from these plates by strips 29 of material which will prevent the passage of electric current while permitting the passage of heat. The thermostat itself is preferably of electrical conducting material, so as to form a conductor beteween the contact 22 and the conductor 24, although equivalent means be employed. l

The conductors 21 and 27 are preferably spring pressed as shown, and are received in sockets 30 and 31 respectively, which are securedto brackets 32 and 33 pivoted upon a sliding block 34 and having .meshing teeth 35 upon their segmentshaped faces 36. The block 34 may be slidably adjusted as by 80 means of an adjusting screw 37 which is held against longitudinal movement by a boss 38, and is threaded into the block 34 as shown. The brackets 32 and 33 may be rotatably adjusted as by means of an adjusting screw 39 which is pivoted to an ear 40 on the block and engages a nut 41 swivelled upon the bracket 33. By this arrangement. the contacts 21 and 27 may be adjusted in unison with respect to the contact 22, and they may also be adjusted with respect to each other, in order to vary the range ot temperature within which the thermostat will act.

In operation, the'parts normally occupy the positions shown in the drawing. Assuming that the plug is applied to an electric ironand the current is then turned on. 1t will be seen that current will pass through n the conductor 7, contact 9, member 13, conductor 19, Sockets 6, between. which is dis- Inc -f thermostat.

posed the heating device, and conductor 8. As the heat ot the device increases, this heat will be transmitted through the plugs of the device to the soclets 6 and thence to the thermostat Q3. This heat will cause the thermostat to iler` to the right as viewed in the drawing, and will thus cause engagement of the contacts Q2 and 2l, the contact 21 yielding to a oid injury to the thermostat. The engagement of these contacts will cause the closing otn one ot the branch circuits of the solenoid and current will flow through the conductor 20, contacts 9.1 and 22, thermostat Q?. conductor 0^- The Ji and the solenoid 17. armature 1G of the solenoid will then actuate the member l?) to diseugage it trom the contacts 9 and 11, thus breaking the heating circuitI and closing at this point the other branch of the solenoid circuit, by causing the member 13 to engage the contacts 10 and 12.

rhe solenoid will be energized for only a mon'ient as the breaking of the heat circuit also breaks the branch ot the solenoid circuit which has caused the above operation. 'Ihe spring 18 will then torce the armature hach to the position shown in the drawing, the pawl 15 riding over the tooth of the ratchet 1%. is the thermostat now cools, the contact may finally engage the Contact QT and thus complete the other branch of the solenoid circuit. the current now passing through the conductor 7. Contact 10, member 13K contact 12 conductor E26, contacts Q7 and 22, thermostat conductor 2st and solenoidl 17. .another quarter turn of the member 13 will be caused, to return the parts to the position shown in the drawing, except that the membei1 13 will be turned end for end to the position from which it started.

From the above, it will be seen that I have provided a plug which may be readily applied to existing fiat irons or other heating devices, without the necessity of making anj.v change in the device itself.

The opening and closing of the various circuits is a positive one, and the thermostat used merely to cause the opening and closing ot the heatingl circuit. The heating current does through the thermostat except momentarily, thereby greatly increasf the lite of the thermostat and the contacts Yciated therewith. The contacts 2l and Q7 may yield as thecontact 22 engages therewith. th preventing undue strain on the By manipulation of the screw the contacts Q1 and 27 may be adjusted in unison without varyingA their relation with respect to each other, and the plug may thus be adjusted to function at the desired temperature. rIhe contacts may then be adjusted with respect to each other, so as to vary the @c of temperature within which the theri will act.

1While I have shown a selected embodiment of my invention, I am aware that various changes in detail may be made, without departing from the spirit ot the invention, and heretore do not intend to limit myself eX- ceptb v the appended claims.

I claim:

1. A plug having means to connect it to a heating device, conductors passing through the plug and adapted to supply current to said device, a switch in one of said concluetors within the plug, a. solenoid adapted to operate said swt-ich, a pair of spaced contacts, a thermostat having a contact disposed between said spaced contacts. and responsive to the heat of said device, and means to operate said solenoid to actuate the switch upon engagement ot' said thermostat contact with ,Y

either one of said spaced contacts.

2. A plug having means to connect it to a heating device, a circuit adapted to supply current to said device, a solenoid having a circuit to supply current thereto, a switch having two pairs ot' oppositely disposed contacts, one ot' said pairs being in one of said circuits and the other of said pairs being in the other ot' said circuits, a contact member adapted to be moved by said solenoid into engagement with the contacts in either of said pairs to close the circuit therethrough, and a thermostat adapted to operate said solenoid and controlled by the heat of said device.

3. A plug having means to connect it to a heating device, conductors passing through the plug and adapted to supply current to said device,` a switch in one of said conductors within the plug, a solenoid adapted to operate said switch and having a circuit in parallel with said heating circuit but normally open. and a thermostat adapted to close said solenoid circuit and controlled by the heat of said device.

at. A plug having means to connect it to al heating device, conductors passing through the plug and adapted to supply current to said device, a solenoid having a. circuit with two branches in parallel with said heating circuit. a switch operated by said solenoid and adapted in one position to close one of said conductors and one of said branches and to open the other of said branches and in another position to close said other of said branches and to open said conductor and said first branch, and a thermostat adapted to close either one ot' said branches to operate the solenoid, said thermostatbeing controlled by the heat ot' said device.

A. plugr comprising sockets adapted to receive plugs on a heating device and spaced apart. a thermostatic element disposed between said sockets and having a contact supported thereon. heat conducting members supporting said thermostatic element and in thermal contact with both the element and the sockets, means electrically7 insulating the III) TIB

GEORGE J. STAVRACOS. 

